Medical electrodes and transdermal patches are well known in the art. Many types of medical electrodes have been introduced in recent years. Typically they comprise: (1) a metallic or electrically conductive carbon terminal member electrically connected to an electro-medical apparatus such as an electrocardiograph; (2) an adhesive tape or pad for holding the terminal member in place on the skin; and (3) an electrically conductive conformable interfacing material such as electrolyte gel or paste over the surface of the terminal member which contacts the skin to reduce skin impedance and to improve electrical contact between the skin and the terminal member. The adhesive may be introduced into the electrically conductive material.
Medical electrodes should not be confused with sensor support bases. Such bases are described, for example, in U.S. Pat. No. 4,947,853, No. 4,947,865, and No. 5,070,880. Such support devices are used in conjunction with Doppler transducers and, hence, are not dependent on electrical conductivity to obtain proper readings. The No. '853 patent and the No. '865 patent relate, for example, to devices for monitoring the contractions of a patient in labor. The No. '880 patent relates to a stabilization device for supporting a transcranial Doppler transducer housing adjacent to the temporal bone of the head. This is useful, for example, for obtaining accurate blood flow velocity measurements. Because none of these devices depend on electrical conductivity to obtain proper readings, the use of an adhesive which is electro-conductive to secure these devices to the patient is completely unnecessary.
Various devices are also known in the art for delivering medication to a patient transdermally. Iontophoretic devices for delivering ionized drugs through the skin have been known since the early 1900's. U.K. Patent No. 410,009 (1934) describes an iontophoretic device which is powered by a galvanic cell and which includes a material containing the drug to be delivered transdermally. The galvanic cell produces the current necessary for iontophoretically delivering the drug.
Today, iontopheresis is not limited solely to the delivery of ions (e.g., drug ions) into the body by means of electric current. For example, it is now recognized that iontopheric delivery devices can be used to deliver an uncharged drug or agent into the body. This is accomplished by a process called electro-osmosis. Electro-osmosis is the transdermal flux of a liquid solvent (e.g., the liquid solvent containing the uncharged drug or agent) which is induced by the presence of an electric field imposed across the skin by the donor electrode. As used herein, the terms "iontopheresis" and "ionopheretic" refer to one or more of (1) the delivery of charged drugs or agents by electromigration, (2) the delivery of uncharged drugs or agents by the process of electro-osmosis, (3) the delivery of charged drugs or agents by the combined processes of electromigration and electro-osmosis, and (4) the delivery of a mixture of charged and uncharged drugs or agents by the combined processes of electromigration and electro-osmosis.
Other transdermal patches do not require electrical power for proper operation. An example of such an item is the Nicotrol transdermal nicotine patch product (Nicotrol is a registered trademark of the Pharmacia AB Corporation). This patch comprises two distinct layers. The layer nearest the patient's skin is a combination of a non-woven polyester and a polyisobutylene and polybutene adhesive. Covering this layer is an impermeable laminated polyester backing layer. This backing layer prevents evaporation of nicotine from, or transmission of light to, the nicotine-containing layer beneath. A layer of adhesive is applied on the impermeable backing layer. The non-woven polyester layer is placed over the adhesive and another adhesive layer is applied over the polyester. The two adhesive layers penetrate the polyester (non-uniformly) to form a single adhesive/polyester composite layer. The nicotine is introduced by printing it on the non-woven polyester layer before the second application of adhesive. Once the patch is applied, the nicotine diffuses out of the adhesive/polyester layer and into the skin of the patient. As sold, the patch includes a release layer which protects the adhesive and which is removed before applying the patch to the skin of the patient.
The removal of medical electrodes or transdermal patches from the skin of patients risks discomfort or pain. A clinician can apply a specific solvent, such as isopropyl alcohol, to help remove the electrode from the skin painlessly. An eye dropper can be used to wet the skin-adhesive boundary while the user simultaneously lifts the edge of the electrode. This approach is slow and cumbersome and it requires a skilled person. The reason for these disadvantages is that the solvent reaches only a small portion of the adhesive at a time and, because the solvent penetrates slowly, the whole process of removal is slow. The uneven distribution of the solvent at the edge of the electrode while lifting it might cause pain to the patient.